Add namespace and labels to go internal metrics

metrics/metrics_runtime.go

@@ -1,12 +1,17 @@
 package metrics
 
 import (
+	"bufio"
+	"bytes"
+	"fmt"
 	"io"
+	"strings"
 
 	vm "github.com/VictoriaMetrics/metrics"
 
 	"github.com/safing/portbase/api"
 	"github.com/safing/portbase/config"
+	"github.com/safing/portbase/log"
 )
 
 func registerRuntimeMetric() error {
@@ -29,6 +34,65 @@ type runtimeMetrics struct {
 }
 
 func (r *runtimeMetrics) WritePrometheus(w io.Writer) {
-	// TODO: Add global labels.
-	vm.WriteProcessMetrics(w)
+	// If there nothing to change, just write directly to w.
+	if metricNamespace == "" && len(globalLabels) == 0 {
+		vm.WriteProcessMetrics(w)
+		return
+	}
+
+	// Write metrics to buffer.
+	buf := new(bytes.Buffer)
+	vm.WriteProcessMetrics(buf)
+
+	// Add namespace and label per line.
+	scanner := bufio.NewScanner(buf)
+	scanner.Split(bufio.ScanLines)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		// Add namespace, if set.
+		if metricNamespace != "" {
+			line = metricNamespace + "_" + line
+		}
+
+		// Add global labels, if set.
+		if len(globalLabels) > 0 {
+			// Find where to insert.
+			mergeWithExisting := true
+			insertAt := strings.Index(line, "{") + 1
+			if insertAt <= 0 {
+				mergeWithExisting = false
+				insertAt = strings.Index(line, " ")
+				if insertAt < 0 {
+					continue
+				}
+			}
+
+			// Write new line directly to w.
+			fmt.Fprint(w, line[:insertAt])
+			if !mergeWithExisting {
+				fmt.Fprint(w, "{")
+			}
+			labelsAdded := 0
+			for labelKey, labelValue := range globalLabels {
+				fmt.Fprintf(w, "%s=%q", labelKey, labelValue)
+				// Add separator if not last label.
+				labelsAdded++
+				if labelsAdded < len(globalLabels) {
+					fmt.Fprint(w, ", ")
+				}
+			}
+			if mergeWithExisting {
+				fmt.Fprint(w, ", ")
+			} else {
+				fmt.Fprint(w, "}")
+			}
+			fmt.Fprintln(w, line[insertAt:])
+		}
+	}
+
+	// Check if there was an error in the scanner.
+	if scanner.Err() != nil {
+		log.Warningf("metrics: failed to scan go process metrics: %s", scanner.Err())
+	}
 }